Two interesting wrinkles turned up. Been going through all my Electra manuals looking for anything on control surfaces and problems.
An Eastern and a Qantas manual both mention that in the event of a loss of authority over any control surface, the best course is to engage the autopilot. The autopilot communicates directly with the boost units, bypassing all the cabling, which of course is where their problem was. But in this incident the autopilot was tagged inoperative. I don't know if that means it was completely nonfunctional with parts yanked, or was in need of adjustment and was considered not trustworthy, so I don't know what would have happened if they turned it on. Investigators suspected that the crew thought the autopilot had engaged and were trying to turn it off, which suggests it was in fact operational but not trustworthy. In any case, they weren't able to take the one recommended course, perhaps because they thought it was the problem.
The second factoid is that in the event of a control surface problem (and only when the autopilot is not available) the default action should be to disconnect the boost for that surface. The Qantas manual says that they can safely cut all boost units in such a case, and recommends it. In a normal flight attitude this would be no problem, but they were in a bank that was getting steeper by the second. Cutting the boost increases the force needed at the flight station, and also reduces considerably the range of movement of the surface, leaving enough movement for what the manuals refer to as normal needs. But in this instance they needed to do full left rudder. So if they followed the manual instructions (presuming NWA specified something along these lines) they were inadvertently crippling their ability to counter the bank using the rudder.
ETA: Just found it in another manual. The movement range with boost off is approximately half for all control surfaces.
Last edited by BRDuBois; 20th Oct 2016 at 17:20.